The present invention is directed to the field of alternator structures in general and more particularly to that portion of the above-noted field which is concerned with the placement of rectifier assemblies within an alternator housing to provide a compact machine for generating a DC output from a rectified AC signal produced by rotary motion. More particularly, the present invention is directed to that portion of the above-noted field which is concerned with the provision of adequate cooling for the rectifier assemblies of such alternators to avoid heat induced failure of the semiconductor rectifier elements. The invention is particularly directed to an alternator structure suitable for use in a motor vehicle electrical system.